1. Evidence for Evolution
4 areas

2. 1. Fossil Record
A fossil is any evidence of an organism that lived years ago.
Paleontologists - scientists who study ancient life & fossils

3. How do fossils form? Most fossils – sedimentary rock
The animal dies & sinks to sea floor or river bottom
The body begins to decay & is buried under layers of sediment (ex. mud or sand). These layers become rock.

4. Rapid burial conditions include:
Beach storm deposits, stream flood deposits, tar/mud pits, volcanic lava flows
Environment determines fossil formation; Very few organisms  fossils

5. Dating Fossils
Relative dating: layers at the bottom are older than those above (approximate age)
Radiometric dating: involves radioactive isotopes C14 & K40 (more exact age)

6. How fossils show evolution
Age & Behavior patterns
Show changes in climate & geography
Shows evolution & adaptation
Problems: Incomplete fossils & Imperfectly preserved

7. Increased food source - vast grasslands
Wider, flatter molars better for eating grass
Grasslands made horses more visible to predators
With hoof-like feet horse can run faster & get away from predators

8. Do you see any similarities among the forelimbs of these animals?
If you said “yes” then you just made a type of observation that scientists use to establish evolutionary relationships among organisms.

9. 2. Anatomy/body structures
Homologous structures = modified structure in different groups of organisms
Similar structure, but may have same/different function
Ex. Bones in forelimbs of vertebrates
Implies common ancestor

11. What is a similar feature of these 2 organisms?

12. Analogous Structures
Structures w/similar function, but different structure
Shows evolution
Ex: wings – bats, insects, & birds
NOT common ancestor
Any body part that is similar in function but different in structure is an analogous structure.

13. Vestigial Structures Structures/organs appear to have little/no use
May have been used in ancestor
Indicate evolution

14. Examples
Ostrich wings
Human appendix
Whales pelvic/hip bones

15. 3. Embryology Many different animals – same organs as embryos
Ex: embryos of fish, reptiles, birds & mammals all have gill slits
Suggests common ancestor
zebrafish chicken dog human skunk

16. 4. Genetic Comparisons Similarities in DNA/RNA sequences
Shows evolutionary relationships
Ex. Organisms use ATP, Same genetic sequences in organisms w/ homologous structures

17. Which 2 insects are most closely related?
Most distantly related?